Sewing machine needle



' Jan. 9, 1968 PRIOR ART 3,362,365 SEWING MACHINE NEEDLE Lothar Recknagel, Albrechts uber Suhl, and Ernst Fischer and Walther Jager, Suhl, Germany, assignors to VEB Zenlrale Entwicklung-Konstruktion fur Eisen-Blechund Metallwaren, Karl-Marx-Stadt, Germany Filed July 8, 1966, Ser. No. 563,858 2 Claims. (Cl. 112-222) This invention relates generally to a sewing machine needle which has a long groove extending axially of the needle. More particularly the invention relates to an improved needle having therein a longitudinal slot or groove which extends past the eye of the needle, and to an impoved method of manufacturing such needles.

In the art of manufacturing sewing machine needles, it is common practice to utilize milling cutters for slotting longitudinal thread retaining grooves in the shank of the needle, after first forming the eye portion of the needle. Though, common, however the practice of slot milling is costly and time consuming, because it is extremely diflicult to accommodate and align the needles properly in the milling machine. Furthermore, since this type of milling operation is not self-adjusting, care must be taken to avoid non-uniformity of the work pieces. This means that costly supervision must be constantly provided to assure efficient production of the needles, and to avoid waste. Also, slot milling is not a precision metal cutting operation. As a result, the milled groove is marred by rough surfaces, milling edges, cutting scale and similar mechanical imperfections which must be removed by a subsequent polishing operation.

Such marring is especially present where longitudinal grooves of rectangular cross-section are milled in needles. Sharp edges and burns result which tend to cut, toughen or even destroy the thread.

Furthermore, needles having such longitudinal grooves in them are weakened, because their cross-sections are materially reduced. To overcome such weakness, it has been proposed to give the needles an elliptical crosssection. However, so changing the cross-section of a round needle shank, combined with the milling operation, creates major technical difficulties; and the resulting increase in stiffness of the needle is negligible. Such needles have not, therefore, been extensively employed.

One object of the invention is, therefore, to form a longitudinal groove in a needle without milling.

Another object is to form such a groove without unduly weakening the needle.

A further object is to avoid the thread cutting, roughening and possible destruction resulting from milled grooves of rectangular cross-section.

According to the invention, a round sewing machine needle, first having its eye formed therein, is pressed between a longitudinally extending punch and a longitudinally extending die to deform a portion of the needle transversely to provide the desired longitudinally extending thread groove therein. The needle may be heated before this groove-forming operation. As a result, a rounded longitudinal thread groove is formed in the needle at the eye therein, and extending longitudinally of the v United States Patent needle away from its eye. At the same time, the metal adjacent the groove is spread radially of the needle so that an outwardly expanding, V-shaped groove is formed with a rounded bottom. The groove-forming operation leaves the longitudinal edges of the needle at the outer end of the groove smoothly rounded.

The invention will be more clearly understood from the following description of one embodiment of the invention, together with the accompanying drawings in which:

FIG. 1 is a cross-section, on an enlarged scale, of a known type of sewing machine needle, having a milled longitudinal thread groove therein of rectangular crosssection, a thread being shown in the groove;

FIG. 2 is a cross-section, on an enlarged scale, of a needle according to the invention with a novel longitudinal thread groove therein, a thread being shown in the groove; and

FIG. 3 is a cross-section, on an enlarged scale, of the needle shown in FIG. 2, together with a diagrammatic representation of the apparatus which is employed to form it.

Referring to the drawings, and in particular to FIG. 1 thereof, a slotted needle 1 of a known cross-section is shown having a milled groove 2 for receiving a sewing thread 3. This known cross-section embodies the particular disadvantageous feature of the sharp milling edges 4, as well as the other disadvantages discussed above respecting this type of needle.

FIG. 2 shows the cross-section of a needle 5 according to the invention, having a V-shaped cross-section and forming a rounded V-shaped thread groove 6 for receiving the thread 3.

The cross-section of the needle 5 at the groove 6 therein comprises two shank portions 7 diverging from the rounded bottom of the groove. Not only the bottom of the groove, but also the shank portions and their ends 8 are smooth becauseof the manner in which the needle is grooved.

In FIG. 3, the manner of grooving the needle 5 is illustrated diagrammatically. Thus, the part of the needle to be grooved is placed longitudinally in a longitudinally extending V-shaped die 9 with a rounded bottom, and a longitudinally extending V-shaped plunger 10 with a rounded leading surface is pressed into the die and against the needle. The longitudinal groove 6 is thus pressed into the needle, the shank portions 7 of the needle being formed by the resulting pressure between the plunger 10 and the die 9. The needle may be heated prior to the groove-forming operation.

Because of the fact that the groove-forming operation is performed entirely by pressure, and without cutting, no sharp edges or burns are formed, and the novel needle 5 will not toughen or cut the thread 3.

The thread groove 6 is edgeless, and since the thread 3 fits precisely therein, a substantial increase in the stitching rate is possible. After thorough testing the needle with the disclosed novel thread groove, it was found that, even though the stitching rate was considerably increased, the needle remained relatively cool. This is so because the thread 3 is able to aid in absorbing a large amount of heat, which develops during the high rate of stitching. Thereby, the needle is prevented from being heated to a temperature at which its hardness and susceptibility to fracture is reduced. Thus, the novel blunt V-shaped cross-section 2. A sewing machine needle as claimed in claim 1, of the needle increases its breakage resistance. wherein said diverging arms are rounded at the edges.

The embodiment of the invention particularly described is presented merely as an example of how the invention may be applied. Other embodiments, forms and modifica- References Cited UNITED STATES PATENTS tions of the invention, coming within the proper scope 360,884 4/1837 Hutchinson F222 of the appended claims, will of course readily suggest 1,042,879 10/1912 Bohin 1r112 222X themselves to those skilled in the art. 35 5 7 1 7 M fi tt What is claimed is: 1. A sewing machine needle having a body portion ex- 10 FOREIGN PATENTS tending longitudinally away from the eye in the form of 21 1,193,006 5/ 1965 Germany.

V-shaped channel having rounded exterior and interior apexes and diverging 21mm RICHARD J. SCANLAN, IR., Primary Examiner. 

1. A SEWING MACHINE NEEDLE HAVING A BODY PORTION EXTENDING LONGITUDINALLY AWAY FROM THE EYE IN THE FORM OF A V-SHAPED CHANNEL HAVING ROUNDED EXTERIOR AND INTERIOR APEXES AND DIVERGING ARMS. 